Whatever you decide, and I favour Canadiangran's advice, consult a lawyer first and either before or after drawing up the will, tell both sons exactly what you have done and why.
I fail utterly to understand why so many people seem to think that adult children should be kept in ignorance, especially if you decide not to leave everything on a fifty-fifty basis.
Let me give an example: my sister's three children, as young adults, borrowed money from their great-aunt, my sister's and my maternal aunt.
My eldest niece repaid the loan well before my aunt's death, keeping strictly to the written agreement she and my aunt had made. Her younger sister had paid off most of her loan, as and when she could, their brother had made no effort at all to repay his.
In the full knowledge of this, my aunt chose not to differentiate between her great-nieces and nephew in her will, leaving the bulk of her money and the flat she owned to them jointly, the contents of the flat to my sister, and only small momentoes to her two godsons, and a small legacy plus momentoes to me.
My eldest niece was hurt that her correct behaviour in repaying a loan as agreed was in no way commended, my sister was hurt at receiving furniture and other household goods that she did not need, nor could easily dispose of and my aunt's godsons, whom my sister and I had known since their birth shortly after ours were desperately hurt at being told they could each choose one personal item from my aunt's home. My sister tried offering them more, but both refused, and neither have spoken to my sister or me since, although we had always beeen on good terms, although the one did attend my sister's funeral.
This sad state of things was not, I am sure, intended by my aunt, so do please take care.